Generally, brake shoes are used mainly for a caliper brake at the bicycle and comprise a shoe body which is elongated in the rotation direction of the wheel rim and which is formed in a rectangular parallelepiped shape having a flat braking surface opposite to the braked surface of the rim. Such brake shoes further include a shoe holder which holds the shoe at the side thereof opposite to the braking surface and which mounts the shoe to each of a pair of brake arms, the shoe body being formed of rubber-like material.
A brake lever is manually operated to actuate the brake arms to allow the shoes to move toward each other and to bring the braking surface of each brake shoe into press-contact with the rim, thereby exerting braking action against rotation of the bicycle wheel.
If a conventional brake shoe, as shown in FIG. 7-(a), is made flat at the braking surface thereof, it is difficult to bring the entire braking surface into press-contact uniformly with the rim, so that surface pressure is not increased with respect to a part of the braking surface to thereby diminish the braking effect to that extent. Also, the braking surface is subjected to surface pressure corresponding in amount only to an input by manually operating the brake lever, in other words, the surface pressure is not more than the input, resulting in less braking effect. The input need only increase in order to raise the surface pressure, but since an increase in the input is limited, it has been impossible to sufficiently raise the surface pressure.
Conventionally, a brake shoe has, as shown in FIG. 7-(b), been proposed which is provided at the shoe body with a plurality of projections each having a braking surface and each being spaced from each other at intervals to form grooves which do not come into contact with each other when braking action is applied.
Such shoe with projections enables the braking surface of each projection to come into press-contact with nearly the entire braked increase in surface of the rim, but the surface pressure is small in percentage. Also, a large space is formed between the rim and the groove so that rain water stays in the space and enters onto the braking surface of each projection to cause a slip between the braking surface of the projection and the braked surface of the rim, thereby resulting in diminished braking effect on a rainy day. Also, the conventional brake shoe occasionally generates noises in good weather.